The present invention relates to the constitution of a stator of a dynamo-electric machine (referred to as a motor hereinafter) used mainly in industrial equipment.
High-density windings and space-saving performance at the ends of windings are increasingly required to realize compact and highly efficient motors. Particularly in order to catch up with the recent trend toward high-speed operation, space-savings, and high output characteristics of a robot, it is necessary to use a magnet of a considerably high magnetic flux density for a rotor of a servo motor of the robot and to increase the winding density of a stator. Although inserter winding has conventionally been practiced to achieve the high density winding, the technique has a demerit in that a large space is consumed at the end of the winding. Nowadays, therefore, the stator is constructed in most cases in such a manner that the core is divided and the winding is wound in alignment outside the stator, thereby achieving a winding with high density and saving space at the end of the winding.
The constitution of a conventional stator will first be described below.
FIG. 3 indicates the constitution of a stator in a first conventional example intended for high-density winding and the saving of space at an end of the winding. In FIG. 3, the reference numerals respectively represent: 21, a first core constituting the outside of a core; 22, a second core constituting the inside of the core; 23, a joint part connecting pole-tooth units of the second core 22 adjacent to each other; 24, an insulator; 25, a winding part; and 26, a resin part.
In the above constitution, the winding part 25 is wound in alignment outside the stator with a high density orthogonally to the insulator 24. A predetermined number of winding parts 25 are inserted into each pole-tooth unit of the second core 22. The second core 22 is then inserted in the inner periphery of the first core 21, thereby constituting a stator core. A stator is hence perfected in the integrated structure when the resin part 26 is formed.
FIGS. 4 and 5 show the constitution of a stator in a second conventional example. In the representative example of the stator in FIGS. 4 and 5, the outer periphery of a layered core is divided in the direction of an output shaft. In FIG. 4, the layered core 31 is divided in half by a dividing face 32. Reference numeral 33 denotes a winding part, and reference numeral 34 of FIG. 5 denotes a resin part.
In the constitution as above, the winding part 33 has a winding orthogonal to the outer periphery of the layered divided core 31. The divided parts of the core 31 are brought to butt against the dividing face 32 and integrated by means of the resin part 34.
The constitution of the first conventional example has disadvantages as follows:
1) Since the core constituting the stator is divided at the outer periphery of the pole-tooth units, the joint part 23 connecting the pole-tooth units at the radial inner peripheries is necessitated to constitute and maintain the second core 22. PA1 2) The magnetism leaks between the pole-tooth units at the joint part 23, lowering the efficiency of the motor. Therefore it is required to make the joint part 23 as thin as possible. PA1 3) Although it is necessary to provide the resin part 26 so as to secure the rigidity in the above constitution of the stator, an insulation coating of the winding part 25 is damaged when the resin part 26 is formed, thereby causing shortcircuiting between wires. PA1 4) In accordance with the increase in size of the core, the pressing and forming plant of the core becomes large in scale, which results in the deterioration of the production efficiency.
According to the constitution of the second conventional example, since the winding part 33 is wound at right angles to the outer periphery of the layered core 31, the winding part 33 cannot be aligned and occupies the conductor merely by 52-55%. Although the space is saved at the end part of the winding, the winding part projects outward in the radial direction, thereby increasing the dimensions of the stator as a whole.